The present invention relates to motor vehicle suspensions in general and more particularly to a bird cage design for mounting wheel axles.
In automotive suspensions, the axles and wheels are connected to the car frame in a way that allows them to move relative to the frame. In some types of racing car suspensions, a device called a "bird cage" is used in making that connection. The bird cage is a frame through which the axle extends. The suspension members and the shock absorber are mounted between the frame of the bird cage and the chassis or frame of the car. The bird cage is adapted to rotate around the axle. This yields certain advantages to the suspension design.
Typically, for a live drive axle design, the drive axle extends from a differential gear through a tube called the axle casing or axle tube. The axle extends out of the casing to be connected to the wheel. The frame of the bird cage telescopes over the axle casing. During use, the axle casing's outer surface rotates and slides against the inner surface of the bird cage. In known designs, a layer of grease provides lubrication between the inside of the bird cage and the outside of the axle casing. One disadvantage in this arrangement is the wear on the axle casing and bird cage due to the rubbing of these parts against each other. The wear is made worse under race conditions by the collection of dirt in the area of the bird cage. This wear can result in grooves and other damage to the axle casing. Wear and contamination can also result in binding of the bird cage against the axle tube which can in turn cause failure of the suspension.